I wouldn't recommend advancing the spark plugs by one....... at TDC the rotor is in the right spot or it's not..... if it's not, re-index the dizzy until it's in the correct spot. If it runs smooth with the advanced timing etc..... doubt it's a flat camshaft.

You need to verify the rotor is at the number one position at TDC on the compression stroke. (see the diagram above) if it's not pull the dizzy out far enough to advane the gear one tooth at a time , drop back in, recheck rotor position, untill it's in the right position.

Verify you have the correct firing order.....18436572 counterclockwise.... looking from the front bumper at the dizzy (unless a 307 which is clockwise)

Verify you have 12v at the coil (dizzy if HEI) while cranking...."I" terminal from starter is the eaisest way to acomplish this